The removal of the mercenaries, the first batch to depart, is taking place in coordination with the UN Libya mission.
Libya's eastern-based forces have agreed to repatriate 300 foreign mercenaries from their area of control after a request from France.
The move is intended to stimulate a UN-backed agreement struck last month between the warring sides in the conflict through a joint military commission to stage a phased withdrawal, the eastern forces official said in a statement on Thursday.
Mercenaries from Russia's Wagner Group are entrenched alongside the eastern-based Libyan National Army (LNA), which was supported in the war by Moscow, along with the United Arab Emirates and Egypt. Turkey sent troops to support the Tripoli government.
The 300 mercenaries would be the first batch to depart and their removal would take place in coordination with the UN Libya mission to prevent destabilisation in the countries they were returning to, the official said.
The official did not say where the mercenaries came from, but said the repatriation would be conducted in coordination with neighbouring countries.
The agreement for the repatriation comes a day before Paris hosts an international conference on the crisis.
The Paris meeting is aimed at securing progress on a planned election and reducing the number of mercenaries and foreign forces.
A ceasefire agreed last year in Geneva called for the removal of all foreign forces and mercenaries in January 2021.
Both sides in Libya's conflict have extensively deployed mercenaries according to UN experts, including from Chad, Sudan and Syria.